Presently, after grinding the receiving surface and depositing a fluxing element, the aforesaid attachment by brazing is performed by placing the element to be brazed on the supporting surface. Then by increasing the temperature of the receiving supporting surface and of the element to be brazed, normally by means of an oxyacetylene blowpipe, the elevated temperature of the elements allows the melted brazing material to flow between the element and supporting surface by capillary action.
This well known and well mastered technique of attachment requires an oxyacetylene unit comprising two bottles, a welding regulator, some pipes and a blowpipe, such unit being voluminous and bulky and it cannot always be transported to work on an outside or field site. Moreover, under certain conditions, and for instance when the supporting surface is solid and a high heat conductor, or when it carries a fluid causing the dissipation of calories, the thermal energy supplied by an oxyacetylene blowpipe is insufficient to bring the supporting surface to the required brazing melting temperature.
This invention aims at eliminating these disadvantages by offering a method of brazing in situ which replaces the calorific supply delivered by the heavy, bulky oxyacetylene unit, such equipment requiring an experience and skill to carry out a good brazing, with a calorific supply produced by a metallothermic reaction.
A method is also known and described in German patent 9825391, to connect two wire conductors end to end consisting, on the one hand, in surrounding the attachment zone with a cartridge containing a metallothermic mixture and, on the other hand, in crushing these melted zones one against the other when the exothermic reaction causes a melting of the wire conductors ends. Such technique, which requires the local melting of the elements to be assembled, requires a large quantity of metallothermic mixture to reach the calorific power necessary for melting. Such method also requires the handling of the elements during the exothermic reaction in order to join them and to reach the compression necessary for their attachment. Thus, such method cannot be applied to the attachment of a conducting wire or jumper on a bulky supporting surface by brazing, and it cannot be applied on an outside site not provided with mechanical means to ensure the compression of the melted zones.
A brazing technique on the site is known and described in German patent 1016096. It consists in attaching a terminal previously placed on a wire conductor on a supporting surface by melting a brazing, said brazing being included in an arrangement of the terminal by means of a metallothermic reaction carried out in a crucible, the wall thereof comprising an opening adapted to the terminal and allowing the direct contact of said terminal with the mixture and the metallothermic reaction.
For such method a special terminal is required for the wire conductor and, after the reaction ensuring the brazing on the site, the crucible has to be withdrawn to disengage the melted metal mass resulting from the reaction and connected to the terminal. This metal mass which does not cooperate with the attachment of the terminal on the supporting surface, forms a protuberance removable only with a file, due to the fact that such melting connection to the back terminal is more resistant than the attachment by brazing of the terminal on the receiver. Such method cannot be used to attach the end of an electric wire conductor or jumper to a metal tube or to any other supporting surface as the proturberance is inconvenient for the installation of a protecting envelope on the connecting zone. Also handling the aforesaid protuberance causes the brazed zone to be caught, and the quality may be altered. Moreover, the positioning of the crucible on the terminal, the latter resting on the supporting surface, requires a particular attention to obtain a good brazing and also requires to provide for different crucibles, whenever the terminal is differently oriented in relation to the supporting surface, or whenever the supporting surface is differently positioned in relation to the vertical plane.
Another brazing technique is shown in French patent publication 2657283 utilizing a metal cup with the attached wire or cable extending into the cup through a hole in the wall. A crucible on top of the cup contains exothermic weld metal which when ignited flows into the cup. The heat from the weld metal provides heat through the bottom wall of the cup to braze the cup to a support surface. The connection provided is bulky, having a substantial protuberance, and is expensive.